Teff grass (Eragrostis tef) is not inherently toxic, but it can pose real health risks to livestock under specific growing and feeding conditions. The biggest concern is nitrate accumulation, which can cause a dangerous blood condition in grazing animals. What makes teff stand out from many other warm-season grasses, though, is what it does not produce: it carries no risk of prussic acid (hydrogen cyanide) poisoning, a hazard well known in sorghum and sudangrass. The full picture of teff grass safety depends on how the forage is grown, harvested, and fed, and on whether you are thinking about horses, cattle, or the grain on your plate.
Nitrate Accumulation Is the Primary Toxicity Risk
Teff, like many fast-growing grasses, can take up more nitrate from the soil than the plant uses for its own growth. Under normal conditions the nitrate levels in teff stay manageable. But drought stress, heavy nitrogen fertilization, cool cloudy weather, or harvesting very young regrowth can push nitrate concentrations into the danger zone. When an animal eats high-nitrate forage, gut bacteria convert the nitrate into nitrite, which enters the bloodstream and changes hemoglobin into a form called methemoglobin that can no longer carry oxygen. The result is a condition called methemoglobinemia, which at severe levels can kill an animal by essentially suffocating it from the inside out.1Journal of Equine Veterinary Science. Effect of Soaking on Nitrate Concentrations in Teff Hay
In cattle, nitrate concentrations above 1% of dry matter are considered highly dangerous, though negative effects have been observed at levels below 0.5%.2Journal of Equine Veterinary Science. Effect of Soaking on Nitrate Concentrations in Teff Hay Horses are somewhat less susceptible to nitrate toxicity than cattle because the microbial conversion of nitrate to nitrite happens mainly in the hindgut rather than the forestomach, so the process is slower and less efficient. That said, horses are not immune. Research evaluating teff alongside other warm-season grasses found high nitrate-nitrogen levels in the forage and recommended testing before putting horses on teff pasture.3Agronomy Journal. Yield, Nutritive Value, and Preference of Annual Warm‐Season Grasses Grazed by Horses
The practical takeaway is straightforward: test your teff hay or pasture for nitrate levels, especially after a drought breaks, after a heavy fertilizer application, or when harvesting the first cutting of a young stand. Forage testing labs are inexpensive and widely available. If nitrate levels come back high, there are still options. Soaking teff hay in water before feeding can reduce nitrate concentrations, and blending high-nitrate hay with low-nitrate feeds dilutes the dose an animal receives at any one meal.
No Prussic Acid Risk, Unlike Sorghum and Sudangrass
This is where teff earns one of its strongest safety credentials. Sorghum, sudangrass, and their hybrids produce a compound called dhurrin, which releases prussic acid (hydrogen cyanide) when plant cells are damaged, such as during wilting, frost damage, or drought stress. Prussic acid poisoning acts fast and can kill livestock within minutes by blocking cells from using oxygen. It is one of the most feared acute toxicity events in pasture management.
Teff does not produce dhurrin. Research comparing teff directly with sorghum-sudangrass forage has noted that teff “combines good forage quality with the absence of dhurrin-related toxicity risk,” making it a safer warm-season option for producers worried about cyanide.4Frontiers in Animal Science. Milk yield and composition of dairy sheep grazing teff or sorghum-sudangrass under Mediterranean summer conditions This is a genuine, unqualified advantage. If you are choosing a summer annual grass and prussic acid is a concern, whether because of unpredictable weather, frost-prone shoulders of the growing season, or limited ability to monitor pastures daily, teff eliminates that particular hazard entirely.
The Inverted Calcium-to-Phosphorus Ratio
A less dramatic but still meaningful concern with teff grass is its mineral balance. Calcium and phosphorus need to be present in a forage in the right proportions for healthy bone and metabolic function, especially in horses. A ratio of roughly 1.5 to 2 parts calcium for every 1 part phosphorus is generally considered ideal for equines. When phosphorus exceeds calcium, the ratio “inverts,” and over time this can lead to problems with bone density and mineral metabolism.
In a study evaluating teff and other warm-season grasses grazed by horses, an inverted calcium-to-phosphorus ratio was observed. The researchers specifically flagged this as something that should be determined before initiating grazing.5Agronomy Journal. Yield, Nutritive Value, and Preference of Annual Warm‐Season Grasses Grazed by Horses This does not mean every cutting of teff hay will have an inverted ratio, but it happens often enough to warrant attention. The fix is usually simple: supplementing with a calcium source like limestone or feeding teff alongside a legume hay such as alfalfa, which is naturally high in calcium. As with nitrates, a forage analysis tells you exactly where you stand before you guess.
Why Teff Is Popular for Metabolically Sensitive Horses
Despite the nitrate and mineral caveats, teff has become a go-to forage for horses that are overweight, insulin-resistant, or at risk of laminitis. The reason is its low nonstructural carbohydrate (NSC) content. NSC includes the sugars and starches in forage that spike blood glucose and insulin after a meal. Horses with equine metabolic syndrome or a history of laminitis need to keep their NSC intake low, and teff typically delivers lower levels of digestible energy, crude protein, and NSC compared to cool-season grasses and alfalfa.
A study comparing horses grazing teff, cool-season grass, and alfalfa found that teff generally had lower digestible energy, crude protein, and NSC than the other forages, and that horses grazing teff during fall had lower peak insulin responses compared to those on cool-season grass.6PubMed. Glucose and Insulin Response of Horses Grazing Alfalfa, Perennial Cool-Season Grass, and Teff Across Seasons For owners managing metabolically challenged horses, this is a meaningful difference. It does not mean teff is automatically safe for every insulin-resistant horse in every cutting and every season, because NSC in any grass varies with growing conditions, time of day, and maturity at harvest. But on average, teff trends in the right direction, and for many horse owners, that trend is the whole reason they are buying it.
This creates an interesting tension: the same forage prized for its low sugar content can simultaneously carry high nitrates under the wrong conditions. Both traits are influenced by growing conditions, but they are independent risks. A batch of teff hay can be wonderfully low in NSC and still have nitrate levels that are unsafe. Testing for both before feeding is the only way to be confident.
Ergot and Mycotoxin Contamination
Teff itself does not produce mycotoxins, but no forage is immune to fungal contamination in the field or in storage. A documented case in South Africa involved severe ergotism in dairy cattle that consumed maize silage and teff hay contaminated with ergot-producing fungus (Claviceps cyperi) originating from nut sedge growing among the crops.7Veterinary Clinics of North America. Mycotoxins Affecting Ruminants Ergot alkaloids constrict blood vessels and can cause tissue death in extremities, convulsions, and abortion. In that case, the toxin came from a weed contaminant rather than from the teff plant itself, but the teff hay served as the vehicle of exposure.
The lesson is not that teff is uniquely susceptible to ergot, because it is not. The lesson is that any hay or silage can carry fungal toxins if weeds, moisture conditions, or storage go wrong. Teff baled at high moisture or stored improperly can develop mold just like any other grass hay. Producers in humid climates, or those making late-season cuttings when dew and rain are harder to avoid, should be especially careful about drying teff adequately before baling. Inspecting bales for mold, off smells, and the dark sclerotia that indicate ergot-infected seed heads is basic due diligence that applies to all forages.
Heavy Metals in Teff Grain Grown on Contaminated Soil
Most toxicity discussions around teff focus on the forage side, but there is a separate concern relevant to teff grain produced for human food. Teff, like many plants, absorbs minerals from the soil it grows in, and not all of those minerals are benign. A study examining teff grown under different soil treatments found that concentrations of cadmium, nickel, and lead in the grain exceeded the permissible levels set by international food safety standards. Cadmium levels in the teff samples ranged from about 97 to 104 mg/kg, far above safe thresholds for human consumption.8Food Chemistry Advances. Nutrient and heavy metal profiling of Teff (Eragrostis tef) under water hyacinth compost and fertilizer treatments using UV-Vis spectroscopy and flame atomic absorption spectroscopy (FAAS)
Before anyone panics about the bag of teff flour in their pantry, context matters. That study used water hyacinth compost as one of its soil amendments, and water hyacinth is well known for accumulating heavy metals from polluted waterways. Teff grown in clean, uncontaminated agricultural soil with conventional or organic fertilizers would not be expected to have those levels. The finding is less a warning about teff itself and more a reminder that any crop grown on polluted soil can become a vector for heavy metal exposure. For consumers, buying teff grain from reputable sources with standard agricultural practices is the practical safeguard.
Anti-Nutritional Factors in Teff as a Food Grain
When people talk about “toxicity” in food grains, they sometimes mean anti-nutritional factors: naturally occurring compounds that interfere with how your body absorbs minerals and nutrients. Teff grain contains phytates and tannins, just like many other whole grains and legumes. Phytates bind to iron, zinc, and calcium in the gut and reduce their absorption, which is one reason why populations relying heavily on unprocessed grain-based diets can develop mineral deficiencies even when their calorie intake is adequate.
Pigmented teff varieties, the darker brown and red types, tend to have higher levels of these phytochemicals than lighter varieties. But calling these compounds purely “anti-nutritional” oversimplifies things, since phytates and tannins also have antioxidant and potentially anti-cancer properties.9International Journal of Food Science and Technology. Teff (Eragrostis tef) processing, utilization and future opportunities: a review Whether they are a net positive or negative depends on the overall diet and how the grain is prepared.
This is where traditional Ethiopian processing comes in. Teff is typically prepared as injera, a fermented flatbread. The lactic acid fermentation involved in making injera batter breaks down a significant portion of the phytates and tannins, improving mineral availability and digestibility. Fermented teff products have higher nutrient availability compared to unfermented preparations, in part because the fermentation process produces beneficial bacteria while degrading the compounds that block mineral absorption.10International Journal of Food Science and Technology. Teff (Eragrostis tef) processing, utilization and future opportunities: a review For people eating teff as a porridge, in baked goods, or in other unfermented forms, soaking the grain before cooking helps reduce phytate levels, much the same way soaking helps with beans and brown rice.
Practical Testing and Management for Livestock Owners
If you are feeding or grazing teff, the risks are manageable once you know what to look for. The two things worth testing every batch of teff hay for are nitrate levels and the calcium-to-phosphorus ratio. Most agricultural extension labs offer both tests as part of a standard forage analysis panel, often for under thirty dollars. If you are buying teff hay specifically for a metabolically sensitive horse, adding an NSC or ethanol-soluble carbohydrate test to the panel is worthwhile too, since the low-sugar reputation of teff does not guarantee every bale will meet the threshold your horse needs.
Timing your harvest helps with nitrate management. Teff cut at a more mature stage generally has lower nitrate concentrations than young, rapidly growing teff. Avoiding harvest immediately after a drought breaks, when the plant has taken up nitrate but not yet metabolized it through growth, is one of the simplest risk-reduction strategies. If a batch comes back high in nitrate, soaking the hay for 30 to 60 minutes and discarding the water can pull out a meaningful portion of the soluble nitrate before feeding.11Journal of Equine Veterinary Science. Effect of Soaking on Nitrate Concentrations in Teff Hay
For the calcium-to-phosphorus issue, the solution is dietary rather than agronomic. Adding a calcium supplement, feeding teff alongside a calcium-rich forage like alfalfa, or using a mineral block designed to correct the ratio are all standard approaches that horse and cattle nutritionists recommend routinely. None of these fixes are unique to teff; they apply any time a grass hay turns up with marginal or inverted mineral ratios.
How Teff Compares to Other Summer Forages on Safety
Viewed against the full menu of warm-season annual grasses, teff’s safety profile is actually one of its selling points. Sorghum, sudangrass, and their hybrids all carry the risk of prussic acid poisoning, which can be lethal within minutes and is nearly impossible to treat in the field. Pearl millet does not produce prussic acid but can accumulate nitrates and oxalates. Bermudagrass and bahiagrass, while perennial rather than annual, have their own issues with endophyte toxins and ergot alkaloids in certain situations.
Teff’s risks, primarily nitrate accumulation and an occasionally inverted mineral ratio, are both detectable through routine testing and manageable through straightforward feeding adjustments. It produces no cyanogenic compounds under any growing condition, does not host the endophyte fungi that plague tall fescue, and its low-sugar profile makes it distinctly useful for a class of animals (metabolically challenged horses) that has limited safe forage options. None of this makes teff risk-free, but it does make it one of the easier warm-season forages to manage safely when you are paying attention to the basics.